574 



A TEXTBOOK OF THEORETICAL BOTANY 



This association is probably symbiotic. The entry of the Fungus happens 

 very shortly after the germination of the spore, and if it does not occur the 

 prothallus never develops more than five cells. There is reason to suppose 

 that the Fungus supplies the tissues with some nutrient material, but the 

 chemistry of the relationship is unknown. 



As a few species of Lycopodium, notably L. cerjiuum, have surface-living 

 prothalli with chlorophyll, it seems probable that the mycorrhizal habit has 

 originated secondarily, with loss of chlorophyll, though whether the under- 

 ground growth is the cause or the effect of the change cannot be ascertained. 



^,,<C^»i'^ •- 



.%l^n^» 



Arche- 



gonium 



Antheridium 



Embryo 



zai layer 



Fig. 583. — Lycopodium clavatum. Vertical section through the 

 prothallus showing mycorrhizal zone and reproductive organs. 

 {After Bruchmann.) 



Development of the Antheridium 



The antheridium arises from a superficial cell of the prothallus. This 

 divides into an inner cell, from which the antherozoid mother cells are 

 formed, and an outer cell which produces the covering layer of the 

 antheridium. The mature antheridium consists of an oval mass of antherozoid 

 mother cells projecting slightly from the prothallial tissue and surrounded 

 by a wall, which is partly formed by the covering layer and partly from 

 prothallial cells (Fig. 584). 



The antherozoids are biflagellate and closely resemble those of the 

 Bryophyta (Fig. 585). This is peculiar to the order Lycopodiales among 

 Pteridophyta and suggests a closer linkage with the Mosses than with the 

 Ferns. The character, though minute, is highly significant from the point 

 of view of relationship, because it is not correlated with any other peculiarity 

 of structure or function in the species. 



